The present invention relates to a rotating electric machine used in traveling drive of an electrically driven vehicle such as an HEV or an EV.
Rotating electric machines used in applications such as home appliance products and various types of OA devices have come to be used in recent years in electrically driven vehicles such as hybrid vehicles (HEVs) and electric vehicles (EVs).
The rotating electric machine for an electrically driven vehicle such as an HEV or an EV in particular, must be able to provide large output. At the rotating electric machine for electrically driven vehicle application, which is engaged in operation over a wide rotation-rate range, the excitation frequency of the electromagnetic exciting force changes over a wide range and the natural frequency of vibration inherent to the structure of the rotating electric machine and the excitation frequency match at a specific rotation rate. For this reason, the occurrence of vibration and noise attributable to resonance is inevitable.
At the same time, there is an ongoing pursuit of improvement in the cabin environment with an attendant increase in the need for lessened vibration and noise. This has led to the development of numerous technologies for reducing vibration and noise originating from the rotating electric machine.
The electromagnetic exciting force, which causes vibration and noise originating from the rotating electric machine, works along three directions, i.e., the radial direction, the tangential direction and the axial direction. In order to reduce noise in the audible band, in particular, the amplitudes of harmonics in such electromagnetic exciting forces must be reduced.
The AC rotating electric machine disclosed in PTL 1, at which the number of slots formed in correspondence to a single pole in a given phase is two, openings (01, 02) at the individual slots are formed so that the intervals between centerlines A extending along the radial direction through slot openings formed next to one another are not uniform and a first three-phase stator winding and a second three-phase stator winding are installed at the stator core with a phase difference of 31° through 34° in electrical angle, succeeds in reducing the electromagnetic sound of 12f components of harmonics and as well as the sound of wind. The number of slots that can be formed at a stator core to adopt this invention is limited by a function of the number of phases and the number of poles, and thus, the technology must be further finessed in order for it to be adopted in stator cores with any numbers of slots free of such restrictions.